Heat generated at a tread portion of a tire when the tire is rotated under load exerted thereon raises temperature at the tread portion, thereby causing various troubles such as heat separation at the tread portion. It is therefore necessary to reduce heat generation or facilitate heat dissipation at a tread portion of a tire in order to decrease temperature at the tread portion.
Conventionally, there has been employed in order to decrease temperature at a tread portion of tire a method of reducing an amount of tread rubber as heat source and increasing surface area of the tread portion to facilitate heat dissipation there by an increase in groove formation at the tread portion (e.g. Patent Literature 1).